Haven't tried one myself (although I, too, am interested), but I keep reading that LEDs, while bright up close, don't project down the road nearly as well as H4's. I have to admit, though, that an LED spotlight I bought recently seems to project well, but it's pretty much a pencil beam with no spread. There's no doubt that LEDs will soon replace H4's etc., but I'm not sure they're there yet. Hopefully someone will do a real test on these H4 replacements soon.

I've seen one being tested by a local retailer. The problem with the H4 LED bulbs is that they do put out quite a bit of heat, and need a fair sized heat sink on the back in order to keep the LEDs in a functional temperature range. This can generate enough heat to melt plastic fairing parts.

The version I saw at the retailer actually had a small fan built into the heatsink to try to mitigate this, but the size of the fan made it extremely difficult to install into a GL1100 headlight bucket. And what happens if the fan motor seizes?

So I would say we're not quite there yet. Purpose-built LED headlights perform amazingly well, but LED retrofit bulbs are nowhere near the performance of much cheaper HID bulbs, and even some quality halogens.

I wondered about the LED replacement bulbs and if any heat was produced. My wife has a bunch of 100W Cree LED's in her sewing room so I went there this morning to check exactly just that. The 100W 120 volt bulb does produce heat at the heat sink area at the base of it. Enough heat that I agree with wingadmin.